Electric furnace.



No. 742,852.' I PATBNTBD Nov. 3, 1903. W. s. FRANKLIN.

ELECTRIC FURNACE.

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No. 742,852. PATENTED NOV. 3, 1903. W. S. FRANKLIN.

ELECTRIC PURNAGE.

APPLIoATIoN FILED Imc. 3, 1900.

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UNITED STATES Patented November 3, 1903.

PATENT OEEICE.

I/VILLIAM S. FRANKLIN, OF SOUTH BETHLEHEM, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO FREDERICK CONLIN, OF BETHLEI-IEM, PENNSYLVANIA.

ELECTRIC FURNACE.

SPECIFICATION forming part of Letters Patent N o. 742,852, dated November 3, 1903.

Application filed December 3,1900. Serial No. 38,490. (No model.)

To a/ZZ whom t may concorre:

Be it known that I, WILLIAM S. FRANKLIN, of South Bethlehem, in the county of Northampton, and in the State of Pennsylvania, have invented certain new and useful Improvements in Electric Furnaces; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, in which- Figure lis a vertical sectional view of a furnace embodying my invention, the upper electrode bein g partly immersed in the molten high-resistance conductor and the furnace being illustrated as applied to the reduction of iron ore. Fig. 2 is a similar view, the upper electrode being positioned above the upper surface of the molten high-resistance conductor; and Figs. 3 and 4 are respectively views similar to Figs. l and 2, illustrating the application of my furnace to glass-making.

Letters of like name and kind refer to like parts in each of the figures.

The object of my invention has been to pro vide an electric furnace of high efficiency; and to such end my invention consists in the electric furnace hereinafter specified.

In carrying my invention into practice I provide a structure A, in which is formed Within the lower portion of such structure a preferablypear-shapedchamberB,which communicates at its upper end with a short cylindrical passage C. The upper end of the passage C opens into a flaring mouth D, by which materials are introduced into the furnace. At a level Well above the bottom of the chamber B a layer of carbon, metal, or other suitable material which is a conductor of electricity, preferably in the form of plates E and E, is built into the structure A, and such layer preferably extends entirely around the circumference of the said chamber. It is not, however, essential that the layer of carbon occupy more than a portion or point of such circumference. If desired, the entire walls of the chamber may be covered with carbon. The portions of the chamber B which are not covered with carbon and also the passage C and mouth D are preferably covered with refractory material. The layer of carbon is connected, as by a terminal e, with a source of electricity and forms one of the electrodes of the furnace. The second electrode is preferably in the form of a rod or bar F of carbon, metal, or other suitable material which is a conductor of electricity, such rod being supported in any suitable manner. I have shown the bar as hung from the strap f of an eccentric f', which is fixed on a shaft f2. The bar F is provided with downwardlyinclined teeth f3 and f3 on its sides. Near the bottom of the chamber B a vent G passes through the walls of the structure A and communicates with such chamber. At a higher level than the vent G a second vent H affords communication with the chamber B through the wall of the structure A. The vents Gand I-I are normally closed. Any convenient form of closure can be used-such, for instance, as a plug of clay.

In the operation of my furnace a portion of the chamber B is filled with a molten electrical conductor I, which has a high electrical resistance. Such materials as slag or glass are suitable for the molten conductor. The current of electricity is made to pass from one electrode to the other through the molten conductor I. rIhe passage of the current through the molten conductor develops a large quantity of heat, owing to the resistance to such passage, and the said conductor is raised to and maintained at a very high temperature. If the upper electrode F be partly immersed in the molten conductor I, as shown in Fig. l, the heat developed will be almost entirely due to the resistance of such conductor. If, however, the upper electrode be raised above the upper surface of the molten conductor, an arc will be formed between such electrode and the said surface, and the heat of such arc will be added to the heat developed by the resistance of the molten conductor.

The furnace can be constructed with the carbon rod partly immersed in the molten conductor, in which case the heat will be generated almost entirely in such conductor, or it can be constructed with the carbon rod above the upper surface of the molten conductor, in which case heat will be generated both by the arc formed between the carbon rod and IOO the molten conductor and by the passage of the current through such conductor, or, as I prefer, it can be constructed so that the carbon rod is vertically adjustable, to permit of the use of the furnace either with or without the arc.

The material to be acted upon by the furnace is introduced into the month D and is fed slowly downward by any suitable means. In the example I have chosen for illustration the feeding is caused by the reciprocation of the carbon rod. As the latter descends the horizontal under surfaces of the teeth f3 and f3 engage the material and carry it downward. When the carbon rod rises, both the action of gravity and the inclined upper surfaces of the teeth f3 and f3 facilitate the passage of the teeth upward through the material without raising the latter, so that on the next downward stroke a fresh quantity of material shall be fed downward. In its downward passage such material is first subjected to the action of the heat ascending from the molten conductor and afterward comes into contact with the highly-heated molten conductor itself. If the upper electrode is raised above the molten conductor, the descending material is also directly acted upon by the arc formed between said electrode and such conductor. If the product resulting from the action of the heat or electricity, or both, on the descending material is of greater specific gravity than the molten conductor, such product will pass through said conductor and collect in the bottom of the receptacle B. During the passage of the said product through the molten conductor the product will be separated from impurities of lighter specific gravity than itself, as such impurities will either float on the surface of the molten conductor or will remain in the body thereof. The product can then be drawn from the lower vent, while the molten conductor can be kept at the proper level by means of the upper vent. If such product is of less specific gravity than the molten conductor, said conductor will occupy the bottom portion of the receptacle B, while the product will accumulate at the level of the upper vent and can be withdrawn therethrough. In such case, if the product be of greater conductivity than the molten conductor, it is desirable not to have thelower electrode extend above the level of the molten conductor.

In using my furnace for the reduction of iron ore the molten conductor I prefer to use is slag. The usual charge containing the ore is fed slowly through the mouth D and passage G into the chamber B. Such feeding can either be in a continuous stream or at intervals, as desired. The latter form of feeding facilitates the adjustment of the quantity of material to be treated to the capacity of the furnace and also enables the charge of ore, coal, limestone, dac., to be fed separately and to be accurately regulated in quantity.

masts As the charge passes downward the ore is reduced during its descent bythe heat ascending from the molten conductor or from such conductor and the arc, according as the carbon rod is immersed ornotin the molten conductor. When the ore reaches the intenselyhot slag, it melts and filters through the slag to the bottom of the receptacle B, where it collects. The iron is drawn off as desired through the lower vent, and the slag is kept at the proper level through the upper vent.

In using my furnace for the making of glass only one vent is necesssary. For such purpose I use glass itself as the molten conductor, the chamber B being filled to the proper level with such material. The raw materials from which the glass is to be formed are fed through the mouth D and passage C into the chamber B. Such materials become heated as they descend until when they reach the surface of the intensely-hot molten glass they are fused and form glass, which is added to the mass of the molten conductor. In constructing the furnace for glass-making it is desirable to line the lower portion of the chamber B with carbon or other conducting material.

In my furnace the heat, being generated in and on the mass of molten conductor, easily reaches a large mass of the material to be acted upon, which is not true of a furnace in which an electric arc alone is used. In the latter case the heat is concentrated in a small zone and is not readily distributed to the mass to be acted upon. IVhen my furnace is used with the carbon rod immersed, the heating electric current passes wholly through the circuit formed only by the electrodes and the molten conductor, and the resistance to such current is substantially uniform. It is therefore necessary in such case to provide automatic means for adjusting the qualities of the current to the resistance of the circuit.

My furnace is adapted to the treatment of other materials than iron ore and glass, and changes which are wit-hin the scope of my invention can be made in the furnace.

Having thus described myinvention, what I claim isl. In an electric furnace, the combination of a structure having a chamber, a molten conductor, electrodes, one of which is above the conductor, but out of contact therewith, to form an arc, and means for reciprocating said electrode to feed into the furnace the material to be treated.

2. In an electric furnace, the combination of a structure having a chamber with an opening in its upper end for the supply of material, electrodes, one of which extends through such opening, said electrode being provided with downwardly-projecting teeth, and means for reciprocating such electrode, whereby the feeding of the material is effected.

3. In an electric furnace, the combination of a structure havinga chamber, a molten con- IOO IIO

ductor therein, electrodes in said chamber, i tact therewith, and means for reciprocating one of which is in contact with said condnosaid latter electrode.

tor, and the other above but ont of contact In testimony that I claim the foregoingr I therewith, and means for reciprocating said have hereunto set my hand this 3d day of Oc- 5 latter electrode. tober, 1000. i

4:. In an electric furnace, the combination l T of a structure havinga chamber, a molten vit- XVM' S' FRAB KLIN' reons conductor therein, electrodes in said Witnesses: chamber, one of which is in Contact With said HOWARD L. BRONSON, xo conductor, and the other above but ont of con- II. XV. BROWN. 

